As shown in a side view of FIG. 1, an existing bicycle driving device 10 includes a socket 11 coupled to a frame, a crankshaft 12 rotatably coupled to the socket, a pair of crank arms 13a, 13b coupled to both sides of the crankshaft 12, and pedals 14a, 14b coupled to ends of the crank arms 13a, 13b. FIG. 2 is a plane view showing the existing bicycle driving device 10.
As shown in FIG. 3, the left pedal 14a rotates while along a circular orbit in a counterclockwise direction on the basis of the crankshaft 12. At this time, when the left pedal 14a is located at a front position (the region from A1 to A3), a rider may apply a force to the crankshaft 12 by the left foot. When the left pedal 14a is located at A2, a strongest force may be applied to the crankshaft 12 in consideration of the principle of levers. Meanwhile, when the left pedal 14a is located at a rear position (the region from A3 to A1), it is impossible to apply a force. When the left pedal 14a is located at a rear position, since the right pedal 14b is located at a front position, a force may be transmitted to the crankshaft 12 by the right foot.
The rotating force transmitted to the crankshaft 12 is greater as the length of the crank arms 13a, 13b is greater. However, in consideration of a body structure of human, the length of the crank arms 13a, 13b is substantially standardized.
Meanwhile, when the left pedal 14a is located at A1 of FIG. 3, if a rider applies a force in a gravity direction by the left foot, the force is entirely transmitted to push the crankshaft 12. If a force is applied to the left pedal 14a in the gravity direction at the position A1, the crankshaft 12 is not rotated.
Meanwhile, when the left pedal 14a rotates in a counterclockwise direction on the basis of A1, it is assumed that a force F perpendicular to the left pedal 14a is applied. At this time, the force of F*sin θ with respect to a rotation angle θ on the basis of the location A1 is transmitted to the crankshaft 12 as a rotation energy. Moreover, since F*cos θ applies a force in a horizontal direction of the crankshaft, the force disappears.
Korean utility model publication No. 20-2009-0000283 (entitled ‘a device for varying a turning radius of a bicycle pedal’) belongs to a field associated with the present disclosure.